is_x.cc

#include <iostream>
#include <type_traits>

template<int A, typename B, typename C>
struct X { };

template<typename T>
struct is_X : std::false_type {};

template<typename... Args>
struct is_X<X<Args...>> : std::true_type {};

int main(int argc, char* argv[]) {
  using my_x = X<0, float, char>;

  std::cout << is_X<my_x>::value << std::endl;

  return 0;
}

include

include <type_traits>

template<int A, typename B, typename C>
struct X { };

template
struct is_X : std::false_type {};

template<int I, typename... Args>
struct is_X<X<I, Args...>> : std::true_type {};

int main(int argc, char* argv[]) {
using my_x = X<0, float, char>;

std::cout << is_X<my_x>::value << std::endl;

return 0;
}